Acrylonitrile-butadiene-styrene (abs) thermoplastic transparent resin

ABSTRACT

The present invention relates to a process for preparing thermoplastic resin for extrusion sheets, and particularly to a process for preparing acrylonitrile-butadiene-styrene (ABS) thermoplastic transparent resin for extrusion sheets having superior impact resistance, chemical resistance, processability, whitening resistance, high temperature elongation, etc. and very superior transparency, by controlling a mixing ratio of a methacrylate alkylester compound or acrylate alkylester compound, an aromatic vinyl compound, and a vinylcyanide compound grafted on conjugated diene rubber latex of which an average particle diameter and gel contents (degree of crosslinking) are optimized to control a refractive index of the monomer mixture to be similar to that of the rubber latex, and optimizing the molecular weight.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a process for preparing thermoplasticresin for extrusion sheets, and more particularly, to a process forpreparing acrylonitrile-butadiene-styrene (ABS) thermoplastictransparent resin having superior impact resistance, chemicalresistance, processability, whitening resistance, high temperatureelongation, etc., and very superior transparency, by controlling amixing ratio of methacrylate or acrylate alkylester compound, aromaticvinyl compound, and vinyl cyanide compound monomers grafted onconjugated diene rubber latex of which an average particle diameter andgel contents (degree of crosslinking) are optimized to control therefractive index of the monomer mixture to be similar to that of therubber latex, and to optimize the molecular weight.

(b) Description of the Related Art

Recently, as industries have advanced and products have becomedifferentiated, studies for developing transparent materials in order tointroduce the nude fashion culture and pastel tone color culture inproducts to achieve design revolution have actively progressed. Forthis, many technologies for introducing an acrylate alkylester ormethacrylate alkylester compound into acrylonitrile-butadiene-styrene(ABS) resin having superior impact resistance, chemical resistance,processability, etc. to give transparency have been developed (U.S. Pat.No. 4,767,833, Japanese Patent Laid-open publication Hei 11-147920, EP703252, Japanese Patent Laid-open Publication No. 8-199007). However,since most of these technologies are aimed at injection-molding productsand thus high temperature elongation or whitening resistance, etc. areinferior, the products are not suitable for extrusion sheets such asexpressway and street transparent soundproofed walls, transparentadvertising panels, transparent bathtub, industrial transparent sheets(covers for machines, industrial transparent windows and doors,canopies, etc.), of which uses are actively being developed.Accordingly, polycarbonate resin or PMMA resin is limitedly used forthese sheets. However, although the polycarbonate resin extrusion sheethas good transparency and impact resistance, it has inferiorprocessability and chemical resistance, etc., and is expensive. Andalthough the PMMA resin extrusion sheet has good transparency, it haslimitations in applications due to a drop in impact resistance, etc.

In addition, ABS resin for extrusion sheets that can be generally usedhas good impact resistance, processability, chemical resistance, hightemperature elongation, etc., but it is an opaque material and thus isnot suitable for transparent extrusion sheet.

SUMMARY OF THE INVENTION

Accordingly, the present invention is made in consideration of theproblems of the prior arts, and it is an object of the present inventionto provide a process for preparing acrylonitrile-butadiene-styrene (ABS)thermoplastic transparent resin having superior impact resistance,chemical resistance, processability, whitening resistance, hightemperature elongation, etc., and very superior transparency, and isthus suitable for extrusion sheets.

In order to achieve the objects, the present invention provides aprocess for preparing acrylonitrile-butadiene-styrene thermoplastictransparent resin comprising the steps of:

a) providing conjugated diene rubber latex; and

b) graft-copolymerizing

i) on 5 to 35 wt % of the a) conjugated diene rubber latex,

ii) 30 to 70 wt % of methacrylate alkylester or acrylate alkylester;

iii) 15 to 30 wt % of an aromatic vinyl compound; and

iv) 0.5 to 20 wt % of a vinyl cyanide compound byemulsion-polymerization.

DETAILED DESCRIPTION AND THE PREFERRED EMBODIMENTS

The present invention will now be explained in detail.

In order to solve the problems of the prior art, the present inventors,as a result of studies, have prepared a thermoplastic transparent resinfor extrusion sheets having very superior transparency and superiorchemical 3 resistance, processability, high temperature elongation,whitening resistance, etc., by introducing a methylmethacrylate alkylester compound; controlling contents of introduced monomers to control adifference between the refractive index of the rubber latex used andthat of a mixture of methacrylate alkylester or acrylate alkylestercompound, aromatic vinyl compound (styrene), acrylonitrile compound,etc. grafted thereon to within 0.005; maintaining a specific molecularweight in order to assure high temperature elongation; and controllinggel contents (degree of crosslinking) and average particle diameter ofthe rubber latex used in order to maintain whitening resistance, whenpreparing ABS resin comprising an acrylonitrile giving superior chemicalresistance, a butadiene giving superior impact resistance, and a styrenegiving superior processability.

In the present invention, the refractive index of the monomer mixtureabsolutely influences transparency, and the refractive index iscontrolled by controlling the mixing ratio of monomers. Specifically,when polybutadiene is used as the rubber latex, since the refractiveindex of the rubber latex is about 1.518, the refractive index of thegrafted ingredients should be controlled to be similar thereto in orderto assure transparency. Thus, the mixing ratio of monomers is veryimportant. For reference, the refractive indexes of each monomer used inthe present invention are as follows: that of methylmethacrylate isabout 1.49; that of styrene is 1.59;and that of acrylonitrile is about1.518.

Accordingly, it is important to control the mixing ratio of monomers sothat the refractive index difference between the conjugated diene rubberlatex and a mixture of the methylmethacrylate alkyl ester compound, thearomatic vinyl compound (styrene), and the vinyl cyanide compound(acrylonitrile compound) grafted thereon may be within 0.005. If therefractive index difference is 0.005 or more, the transparency will dropand the object of the present invention cannot be achieved.

As the polymerization method, bulk polymerization, solutionpolymerization, suspension polymerization, etc. can be used, but sincethese methods must use a rubber with a large particle diameter, and thuswhitening resistance is inferior and a polymer with a large molecularweight is difficult to obtain, emulsion polymerization is preferable.

The acrylonitrile-butadiene-styrene thermoplastic transparent resincomprises a conjugated diene rubber latex and monomers grafted thereon,i.e., a methacrylate alkylester compound, an aromatic vinyl compound,and a vinyl cyanide compound, and it is prepared by emulsionpolymerization.

As a method for graft-adding each ingredient, a batch introducing methodand a continuously (sequentially) introducing method can be used. Thepresent invention uses a complex type controlling batch introducingmethod and a continuous introducing method.

The molecular weight of the graft copolymer obtained in the presentinvention is preferably 75,000 to 300,000, and more preferably 80,000 to290,000. If the molecular weight is less than 75,000, high temperatureelongation is inferior, and if it is more than 300,000, processabilityis inferior.

A process for preparing ABS thermoplastic transparent resin will beexplained in more detail.

a) Process for Preparing Conjugated Diene Rubber Latex

The conjugated diene rubber latex used in the present invention has anaverage particle diameter of 1900 to 5500 Å, preferably 2000 to 5000 Å,gel contents of 50 to 95%, and a swelling index of 8 to 60. If theaverage particle diameter is less than 1900 Å, impact resistance willdrop, and if it is more than 5500 A, whitening resistance is not good.Also, if the gel contents are less than 49%, whitening resistance willdrop, and if it is more than 99%, impact resistance is not good.

As the conjugated diene rubber latex, polybutadiene, butadiene-styrenecopolymer (SBR), butadiene-acrylonitrile copolymer (NBR),ethylene-propylene copolymer (EPDM), and polymers similar thereto can beused, and polybutadiene or butadiene-styrene copolymer is preferable,and polybutadiene is more preferable.

One example of preparation of the polybutadiene rubber latex is asfollows.

According to the present invention, 100 weight parts of 1,3-butadiene, 1to 4 weight parts of an emulsifier, 0.2 to 1.5 weight parts of apolymerization initiator, 0.5 weight parts of an electrolyte, 0.1 to 0.5weight parts of a molecular weight controlling agent, and 75 weightparts of ion-exchange water are batch-introduced andemulsion-polymerized to prepare polybutadiene rubber latex having anaverage particle diameter of 2000 to 5000 Å, gel contents of 50 to 98%,and a swelling index of 8 to 60.

The emulsion polymerization is preferably conducted at 65 to 85° C. for25 to 50 hours.

The emulsifier is selected from the group consisting of alkyl arylsulfonate, alkali methyl alkyl sulfate, sulfonated alkylester, fattyacid soap, an alkali salt of rosin acid, and a mixture thereof.

As the polymerization initiator, a water-soluble persulfate or peroxycompound can be used, and an oxidation-reduction type can also be used.A preferable water-soluble persulfate is sodium persulfate or potassiumpersulfate. Also, a liposoluble polymerization initiator selected fromthe group consisting of cumene hydroperoxide, diisopropylbenzenehydroperoxide, azobis isobutylnitrile, tert-butyl hydroperoxide,paramethane hydroperoxide, benzoylperoxide, and a mixture thereof can beused.

The electrolyte is selected from the group consisting of KCl, NaCl,KHCO₃, NaHCO₃, K₂CO₃, Na₂CO₃, KHSO₃, NaHSO₃, K₄P₂O₇, K₃PO₄, Na₃PO₄,K₂HPO₄, Na₂HPO₄, and a mixture thereof.

As the molecular weight controlling agent, mercaptan is preferable. 20The emulsion polymerization temperature is very important forcontrolling the gel contents and swelling index of rubber latex, and theselection of an initiator should also be considered.

b) Process for Preparing Graft Copolymer

According to the present invention, a monomer mixture of 30 to 70 wt %of a methacrylate alkyl ester compound or an acrylate alkylestercompound, 15 to 30 wt% of an aromatic vinyl compound, and 0.5 to 20 wt %of a vinylcyanide compound is graft-copolymerized on 5 to 35 wt % of theconjugated diene rubber latex (preferably, polybutadiene rubber latex)by emulsion polymerization to prepare an acrylonitrile-butadiene-styrenegraft copolymer. The graft copolymerization is conducted by adding 0.2to 0.6 weight parts of an emulsifier, 0.2 to 0.6 weight parts of amolecular weight controlling agent, and 0.05 to 0.3 weight parts of apolymerization initiator, on the basis of 100 weight parts of themonomer mixture.

The graft copolymerization is preferably conducted at 65 to 80° C. for 4to 7 hours.

The methacrylate alkylester or acrylate alkylester compound ispreferably one or more kinds selected from the group consisting ofmethyl methacrylate, ethyl methacrylate, methyl acrylate, and aderivative thereof.

The aromatic vinyl compound is preferably one or more kinds selectedfrom the group consisting of styrene, α-methyl styrene, o-ethyl styrene,p-ethyl styrene, vinyl toluene, and derivatives thereof.

The vinyl cyanide compound is preferably one or more kinds selected fromthe group consisting of acrylonitrile, methacrylonitrile,ethacrylonitrile, and derivatives thereof.

The emulsifier is preferably selected from the group consisting ofalkylaryl sulfonate, alkali methylalkyl sulfate, sulfonate alkylester,fatty acid soap, an alkali salt of rosin acid, and a mixture thereof.

As the molecular weight controlling agent, tert-dodecyl mercaptan ispreferable.

As the polymerization initiator, peroxides such as cumene hydroperoxide,diisopropylbenzene hydroperoxide, and a persulfate can be used; and anoxidation-reduction catalyst selected from the group consisting ofsodium formaldehyde sulfoxylate, sodium ethylenediamine tetraacetate,ferrous sulfate, dextrose, sodium pyrophosphate, sodium sulfite, and amixture thereof can be used.

After polymerization is terminated, the polymerization conversion rateis preferably 98% or more, and an anti-oxidant and stabilizer may beadded to the latex and coagulated with calcium chloride an aqueoussolution at 80 ° C. or more, and then dehydrated and dried to obtain apowder. Stability of the prepared graft copolymer latex can be judged bymeasuring solid coagulation contents (%) using Equation 1:$\begin{matrix}{{{Solid}{\quad\quad}{coagulation}\quad{contents}\quad(\%)} = {\frac{{Weight}\quad{of}\quad{produced}\quad{coagulated}\quad{substance}\quad(g)}{{Weight}\quad{of}\quad{total}\quad{rubber}\quad{and}\quad{monomers}\quad(g)} \times 100}} & \lbrack {{Equation}\quad 1} \rbrack\end{matrix}$

In Equation 1, when the solid coagulation contents are 0.7% or more, thestability of the latex seriously drops, and a graft copolymer suitablefor the present invention cannot be obtained due to a large amount ofthe coagulated substance.

An antioxidant and a stabilizer are introduced into the obtained powderand then a pellet is prepared at 200 to 230° C. using a 2-shaftextrusion kneader, and the pellet is injection-molded again to measureits physical properties.

As explained, the mixing ratio of monomers is very important to obtainthe transparent resin, and the refractive index differs according to themixing ratio. Specifically, since the refractive index of polybutadienerubber latex is about 1.518, the total refractive index of compoundsgrafted thereon should be similar thereto, and if the difference is0.005 or more, transparency drops and thus it is not suitable for thepresent invention. Therefore, according to the present invention, an ABSthermoplastic resin is produced having superior impact resistance,chemical resistance, processability, whitening resistance, and hightemperature elongation, and very superior transparency, and is thussuitable for manufacturing extrusion sheets.

The present invention will be explained in more detail with reference tothe following Examples. However, these are to illustrate the presentinvention, and the present invention is not limited to them.

Example 1

1) Process for Preparing Polybutadiene Rubber Latex

To a nitrogen-substituted polymerization reactor (autoclave), 80 weightparts of ion-exchange water, 100 weight parts of 1,3-butadiene, 1.2weight parts of potassium rosinate as an emulsifier, 1.5 weight parts ofpotassium salt, 0.7 weight parts of sodium carbonate (Na₂CO₃) as anelectrolyte, 0.8 weight parts of potassium bicarbonate (KCHO₃), and 0.3weight parts of tert-dodecylmercaptan (TDDM) as a molecular weightcontrolling agent were batch-introduced, and the reaction temperaturewas elevated to 65° C. Then, 0.3 weight parts of potassium persulfate asan initiator were batch-introduced to initiate reaction, the reactiontemperature was elevated to 85° C. for 35 hours, and then reaction wasterminated and the obtained rubber latex was analyzed, as follows.

Gel Contents (Degree of Crosslinking) and Swelling Index

The rubber latex was coagulated using diluted acid or metal salt, andwashed and dried in a vacuum oven of 60° C. for 24 hours. Then, theobtained rubber mass was cut into tiny pieces, and 1 g of rubberfragments was put into 100 g of toluene and stored in a darkroom at roomtemperature for 48 hours. The resultant was then separated into sol andgel, and the gel contents and swelling index were determined as follows:${{Gel}\quad{contents}\quad(\%)} = {\frac{{Weight}\quad{of}\quad{insoluble}\quad{contents}\quad({gel})}{{Weight}\quad{of}\quad{sample}} \times 100}$${{Swelling}\quad{index}} = \frac{{Weight}\quad{of}\quad{swollen}\quad{gel}}{{Weight}\quad{of}\quad{gel}}$Particle Diameter

The particle diameter of the rubber latex was measured by a laser lightscattering method using a Nicomp 370 HPL (U.S. Nicomp Company product).

The gel contents of the obtained rubber latex was 85%, the swellingindex was 15, and the average particle diameter was about 2800 Å.

2) Process for Preparing Graft Copolymer

A thermoplastic resin was prepared with the composition and contents asshown in Table 1.

In the first step, 18 weight parts of the prepared polybutadiene rubberlatex, 90 weight parts of ion-exchange water, 0.2 weight parts of asodium oleate emulsifier, 18.24 weight parts of methylmethacrylate, 7.09weight parts of styrene, 2 weight parts of acrylonitrile, 0.1 weightparts of tert-dodecylmercaptan, 0.048 weight parts ofsodiumpyrophosphate, 0.012 weight parts of dextrose, 0.001 weight partsof ferrous sulfate, and 0.04 weight parts of cumene hydroperoxide werebatch-introduced at 40° C. into a nitrogen-substituted polymerizationreactor, and reacted while elevating the reaction temperature to 73° C.over 2 hours.

Then, in the second step, a mixed emulsion solution of 70 weight partsof ion-exchange water, 0.4 weight parts of sodium oleate, 36.48 weightparts of methylmethacrylate, 14.19 weight parts of styrene, 4 weightparts of acrylonitrile, 0.15 weight parts of tert-dodecylmercaptan,0.048 weight parts of sodium pyrophosphate, 0.012 weight parts ofdextrose, 0.001 weight parts of ferrous sulfate, and 0.10 weight partsof cumene hydroperoxide were continuously introduced therein for 4hours, and then the temperature was elevated to 76° C., the reactant wasaged for 1 hour, and the reaction was terminated. The polymerizationconversion rate was 99.5%, and the solid coagulation contents were 0.1%.The latex was coagulated with a calcium chloride aqueous solution andwashed to obtain a powder, and the weight average molecular weight andphysical properties were measured as follows.

a) Measurement of Weight Average Molecular Weight

The obtained powder was agitated in an acetone solution for 24 hours,and the acetone-insoluble rubber ingredient and acetone-solublecopolymer were separated using a centrifuge to measure the weightaverage molecular weight of the acetone-soluble copolymer with a GPCusing PS as a standard. The molecular weight of the obtained copolymerwas 150,000.

b) Measurement of Physical Properties

An antioxidant and stabilizer were introduced into the obtained powder,and then a pellet was prepared at 200 to 230° C. using a 2-shaftextrusion kneader, and the pellet was injection-molded again to measurephysical properties thereof by the ASTM method. The results are shown inTable 1.

a) Measurement of Whitening Resistance

A sample for measuring tensile strength obtained by injection moldingwas bent by hand, and the degree of low blush property was evaluatedwith the naked eye. Whitening resistance was good so it was found to beusable, as shown in Table 1.

d) High Temperature Elongation Experiment

A pellet was extruded with a sheet extruder to make its thickness 1.8mm, and then elongation was measured at 150° C. with an elongationtester with the cross-head-speed of the sample set at 200 mm/min. Theresults are shown in Table 1.

e) Surface Appearance

The extrusion pellet was extruded with a sheet extruder to make itsthickness 1.8 mm, and then whether or not its surface was regularlymaintained was confirmed by evaluation as follows. The results are shownin Table 1.

G: Surface thickness is regular and no flowmarks on surface

N.G.: Surface thickness is irregular and flowmarks exists on surface

Comparative Example 1

A thermoplastic resin was prepared by the same process as in Example 1,except that the reaction time was 22 hours instead of 35 hours in theprocess for preparing the rubber latex. The average particle diameter ofthe rubber latex was about 1800 Å, gel contents were about 93%, and theresults of physical property tests are shown in Table 1.

Comparative Example 2

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the rubber latex, the reactiontime was 70 hours instead of 35 hours, and reaction temperature waschanged to 68° C. instead of elevating to 85° C. The average particlediameter of the rubber latex was about 5500 Å, gel contents were about60%, and the results of physical property tests are shown in Table 1.

Comparative Example 31

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the rubber latex, the reactiontime was 60 hours instead of 35 hours, and the reaction temperature wasmaintained at 65° C. instead of elevating to 85° C., and the contents ofthe TDDM molecular controlling agent was 0.5 weight parts instead of 0.3weight parts. The average particle diameter of the rubber latex wasabout 4200 Å, gel. contents were about 45%, and the results of physicalproperty tests are shown in Table 1.

Comparative Example 4

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the graft copolymer, thecontents of methyl methacrylate used in the second step were 33.7 weightparts instead of 36.48 weight parts, and the contents of styrene were 17weight parts instead of 14.19 weight parts. The results for physicalproperty tests are shown in Table 1.

Comparative Example 5

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the graft copolymer, thecontents of methylmethacrylate used in the second step were 41 weightparts instead of 36.48 weight parts, and the contents of styrene were9.6 weight parts instead of 14.19 weight parts. The results for physicalproperty tests are shown in Table 1.

Comparative Example 6

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the graft copolymer, thecontents of tert-dodecylmercaptan used in the second step were 0.01weight parts instead of 0.15 weight parts. The results for physicalproperty tests are shown in Table 1. The molecular weight of theprepared graft copolymer was about 300,000.

Comparative Example 7

A thermoplastic resin was prepared by the same process as in Example 1,except that in the process for preparing the graft copolymer, thecontents of tert-dodecylmercaptan used in the second step were 0.45weight parts instead of 0.15 weight parts. The results for physicalproperty tests are shown in Table 1. The molecular weight of theprepared graft copolymer was approximately 50,000.

Experiment

To 100 weight parts of the graft copolymers prepared in Example 1 andComparative Examples 1 to 7, 0.1 weight parts of a lubricant and 0.2weight parts of an antioxidant were introduced, and a pellet wasprepared at a cylinder temperature of 210° C. using a 2-shaft extrusionkneader. The pellet was injection molded to prepare a sample, and thephysical properties were measured. The results are shown in Table 1.TABLE 1 High temperature elongation Surface Whitening Impact Haze (150°C.) appearance resistance resistance Example 1 2.1 1900 G Usable 16 Com-1 1.9 1700 G Usable 5 parative 2 5.4 2000 G Unusable 19 Exam- 3 4.0 2100G Unusable 18 ple 4 16.7 1950 G Usable 15.5 5 18.9 1850 G Usable 16.5 62.8 2300 G Usable 16.5 7 2.0 500 N.G Usable 12.5

As shown in Table 1, Example 1 showed very superior high temperatureelongation, surface appearance, whitening resistance, and impactresistance by using a conjugated diene rubber latex of which theparticle diameter and gel contents, etc. were controlled, and bycontrolling the ratio of the monomer mixture grafted thereon. On thecontrary, Comparative Examples 1 to 7 showed generally inferior physicalproperties, and specifically, Comparative Example 1 showed a drop inimpact resistance, Comparative Examples 2 and 3 showed a drop inwhitening resistance Comparative Examples 4 and 5 showed a drop intransparency, Comparative Example 6 showed inferior processability, andComparative Example 7 showed inferior high temperature elongation.

As explained, the ABS thermoplastic resin prepared according to thepresent invention has superior impact resistance, chemical resistance,processability, whitening resistance, and high temperature elongation,and very superior transparency, and thus it is suitable formanufacturing extrusion sheets.

1. A process for preparing acrylonitile-butadiene-styrene thermoplastictransparent resin for extrusion sheets, comprising the steps of: a)providing conjugated diene rubber latex; and b) graft copolymerizing i)5 to 35 wt % of the a) conjugated diene rubber latex, ii) 30 to 70 wt %of methacrylate alkytester or acrylate alkyl ester; iii) 15 to 30 wt %of an aromatic vinyl compound; and iv) 0.5 to 20 wt% of a vinyl cyanidecompound by emulsion-polymerization, c) adding 0.2 to 0.5 weight part ofa molecular weight controlling agent on the basis of 100 weight parts ofthe monomer mixture into the monomer mixture to regulate a weightaverage molecular of the acrylonitrile-butadiene-styrene thermoplastictransparent resin in a range of 100.000 to 200,000 such that theacrvtonitrile-butadiene-styrene thermoplastic transparent resin issuitable for an extrusion process.
 2. The process for preparingacrylonitrile-butadiene-styrene thermoplastic transparent resin forextrusion sheets according to claim 1, wherein a difference between therefractive index of the b) i) conjugated diene rubber latex and that ofa mixture of the b) ii) methacrylate alkylester or acrylate alkylestercompound, the b) iii) aromatic vinyl compound, and the b) iv)vinylcyanide compound is within 0.005.
 3. The process for preparingaorylonitrite-butadiene-styrene thermoplastic transparent resin forextrusion sheets according to claim 1, wherein the conjugated dienerubber latex has a average particle diameter of 2000 Å to 5000 Å, gelcontents of 50 to 98%, and a swelling index of 8 to
 60. 4. The processfor preparing acrylonitrile-butadiene-styrene thermoplastic transparentresin for extrusion sheets according to claim 1, wherein the conjugateddiene rubber latex is selected from the group consisting ofpolybutadiene, butadiene-styrene copolymer (SBR), butadiene-acronitrilecopolymer (NBR), ethylene-propylene non-conjugated diene rubber (EPDM),and a rubber latex similar thereto.
 5. (canceled)
 6. The process forpreparing acryfonitrile-butadiene-styrene thermoplastic transparentresin for extrusion sheets according to claim 1, wherein themethacrylate alkyl ester or acrylate alkyl ester compound is one or morekinds selected from the group consisting of methyl methacrylate, ethylmethacrylate, methylacrylate, and a derivative thereof.
 7. The processfor preparing acrylonitrile-butadiene-styre thermoplastic transparentresin for extrusion sheet according to claim 1, wherein the aromaticvinyl compound is one or more kinds selected from the group consistingof styrene, α-methyl styrene, o-ethyl styrene, ρ-ethyl styrene, vinyltoluene, and a derivative thereof.
 8. The process for preparingacrylonitrile-butadiene-styrene thermoplastic transparent resin forextrusion sheet according to claim 1, wherein the vinyl cyanide compoundis one or more kinds selected from the group consisting ofacrylonitrile, methacrylonitrile, ethacrylonitrile, and a derivativethereof.
 9. The process for preparing acrylonitrile-butadiene-styrenethermoplastic transparent resin for extrusion sheets according to claim1, wherein the graft polymerization is conducted by further adding 0.2to 0.6 weight parts of an emulsifier, and 0.05 to 0.3 weight parts of apolymerization initiator, on the basis of 100 weight parts of themonomer mixture.
 10. The process for preparingacrylonitrile-butadiene-styrene thennoplastic transparent resin forextrusion sheets according to claim 1, wherein the b) graftcopolymerization is conducted at 65 to 80° C. for 4 to 7 hours.